Projection apparatus and color-level correcting method therefor

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 94126312, filed on Aug. 3, 2005. All disclosure of the Taiwan application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a projection apparatus and correcting method therefor. More particularly, the present invention relates to a projection apparatus, an illumination module and a color-level correcting method therefor.

2. Description of the Related Art

Referring to <figref idrefs="DRAWINGS">FIGS. 1A and 1B</figref>, a conventional projection apparatus <b>100</b> comprises an optical engine <b>110</b> and a projection lens <b>120</b>. The optical engine <b>110</b> includes a light source <b>112</b>, a color wheel <b>114</b>, a controlling unit <b>116</b> and a light valve <b>118</b>. The light source <b>112</b> is suitable for providing a light beam <b>112</b><i>a </i>and the color wheel <b>114</b> is configured between the light valve <b>118</b> and the light source <b>112</b>. Furthermore, the controlling unit <b>116</b> is electrically connected to the color wheel <b>114</b> and the light valve <b>118</b>.

The color wheel <b>114</b> has a red filtering region R, a green filtering region G and a blue filtering region B. The controlling unit <b>116</b> is suitable for controlling a rotational speed of the color wheel <b>114</b>. The light beam <b>112</b><i>a </i>provided by the light source <b>112</b> passes through the red, the green and the blue color-filtering regions R, G, B in turn to produce red light, green light and blue light. In addition, the light valve <b>118</b> is driven by the controlling unit <b>116</b> to present different states corresponding to the red, green and blue light. Hence, red, green and blue light are converted into red image, green image and blue image respectively. Thereafter, the projection lens <b>120</b> projects the red, green and blue image onto a screen and produce a full color image onto the screen.

In the conventional projection apparatus <b>100</b>, a signal transmitting device <b>117</b> is normally disposed on the color wheel <b>114</b>. Furthermore, a signal sensing device <b>119</b> is also installed at a suitable distance away from the signal transmitting device <b>117</b> for receiving the signal <b>117</b><i>a </i>transmitted from the signal transmitting device <b>117</b>. The signal transmitting device <b>117</b> follows the rotation of the color wheel <b>114</b>, so that a time interval between two received signals from the signal transmitting device <b>117</b> selecting by the signal sensing device is a rotational period of the color wheel <b>114</b>. Moreover, the signal sensing device <b>119</b> and the controlling unit <b>116</b> are electrically connected so that a rotational frequency of the color wheel <b>114</b> is computed through the controlling unit <b>116</b>. Therefore, the passing time for the light beam <b>112</b><i>a </i>through the red, greens and blue color-filtering regions R, G, B is computed.

However, slight positional error often occurs in a process of attaching the signal transmitting device <b>117</b> to the color wheel <b>114</b>. Thus, the controlling unit <b>116</b> can not accurately compute the respective intervals for the passing time of the light beam <b>112</b><i>a </i>through the red, green and blue color-filtering regions R, G and B for controlling the light valve <b>118</b>. As a result, the color of the image projected by the projection apparatus <b>100</b> can not have expected color. At present, one solution is to store a color wheel index in the controlling unit <b>116</b> so that the any timing discrepancies between the color wheel <b>114</b> and the light valve <b>118</b> can be compensated by referring to the color wheel index. With suitable compensation, the timing error is reduced and the image projected from the projection apparatus <b>100</b> is more in line with the expected image colors.

The conventional projection apparatus <b>100</b> normally has only single color wheel index. However, the signals input into the projection apparatus <b>100</b> have different resolutions or vertical synchronous scanning frequencies. Furthermore, the rotational speed of the color wheel changes according to the frequency of the input signal. Therefore, using just one single color wheel index, it is still impossible to compute the intervals for the passage of the light beam <b>112</b><i>a </i>through the red, green and blue color-filtering regions R, G and B. Ultimately, the conventional projection apparatus <b>100</b> leads to some ruggedness in the color level of the projected image from the projection apparatus <b>100</b>.

SUMMARY OF THE INVENTION

One objective of the present invention is to provide an illumination module having a good color level performance.

Another objective of the present invention is to provide a color level correcting method for correcting a projection apparatus so that the color level performance of an image projected from the projection apparatus can be improved.

Still another objective of the present invention is to provide a projection apparatus capable of automatically adjusting a color wheel index according to different input signal so that a color level performance of an image projected from the projection apparatus can be improved.

To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the present invention provides an illumination module. The illumination module comprises a light source, a color wheel and a controlling unit. The light source is suitable for providing a light beam. The color wheel is disposed on an optical path of the light beam. The controlling unit is connected to the color wheel. Furthermore, a plurality of color wheel indices is stored in the controlling unit. When the illumination module receives an image signal, the controlling unit selects one of the color wheel indices according to the image signal.

The present invention also provides a projection apparatus. The projection apparatus comprises a projection lens, an imaging unit and the aforementioned illumination module. The projection lens is disposed on the optical path of the light beam provided by the aforementioned light source. The imaging unit is disposed between the illumination module and the projection lens and electrically connected to the aforementioned controlling unit.

The present invention also provides a color level correcting method for correcting the color level performance of a projection apparatus including a color wheel. The steps of the color level correcting method include inputting a plurality of color wheel indices into the projection apparatus. Then, an image signal is input in the projection apparatus. Thereafter, according to the frequency of the image signal, one of the color wheel indices is selected for controlling the projection apparatus.

In the present invention, a plurality of color wheel indices corresponding to the image signal at different frequencies is stored inside the projection apparatus. Hence, the projection apparatus can automatically select an appropriate color wheel index according to the received image signal so that the tint and color level performance of the picture projected from the projection apparatus can be improved.

It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

<figref idrefs="DRAWINGS">FIG. 1A</figref> is a diagram showing a conventional projection apparatus.

<figref idrefs="DRAWINGS">FIG. 1B</figref> is a diagram showing a color wheel of the <figref idrefs="DRAWINGS">FIG. 1A</figref>.

<figref idrefs="DRAWINGS">FIG. 2</figref> is a diagram showing a projection apparatus according to one preferred embodiment of the present invention.

<figref idrefs="DRAWINGS">FIG. 3</figref> is a flow diagram showing steps for correcting the color level of a projection apparatus according to one preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

As shown in <figref idrefs="DRAWINGS">FIG. 2</figref>, a projection apparatus <b>200</b> comprises an illumination module <b>210</b>, a projection lens <b>220</b> and an imaging unit <b>230</b>. The illumination module <b>210</b> further comprises a light source <b>212</b>, a color wheel <b>214</b> and a control unit <b>216</b>. The light source <b>212</b> provides a light beam <b>212</b><i>a</i>. Furthermore, the light beam <b>212</b><i>a </i>is a white light beam, for example. In one embodiment, the light source <b>212</b> is a mercury lamp, a light-emitting diode (LED), a metallic halide lamp, a halogen lamp or a high intensity discharge (HID) lamp, for example.

The projection lens <b>220</b> is disposed on an optical path of the light beam <b>212</b><i>a </i>and the imaging unit <b>230</b> is disposed between the illumination module <b>210</b> and the projection lens <b>220</b>. Furthermore, the imaging unit <b>230</b> comprises an integrating rod <b>234</b>, a converging lens <b>236</b>, a total internal reflection prism <b>238</b> and a light valve <b>239</b>, for example.

After the light beam <b>212</b><i>a </i>provided by the light source <b>212</b> passing through the color wheel <b>214</b>, the light beam <b>212</b><i>a </i>is converted into a monochromatic light beam <b>211</b>. For example, the color wheel <b>214</b> includes a red color-filtering region R, a green color-filtering region G and a blue color-filtering region B (as shown in <figref idrefs="DRAWINGS">FIG. 1B</figref>) so that the light beam <b>212</b><i>a </i>is converted into the various monochromatic light beams <b>211</b> (red, green, blue). Obviously, the color wheel <b>214</b> also includes a white color-filtering region (not shown). After the light beam <b>212</b><i>a </i>passing through this white color-filtering region, the light beam <b>211</b> remains a white beam.

The monochromatic light beam <b>211</b> passes through the integrating rod <b>234</b>, the converging lens <b>236</b>, the total internal reflection prism <b>238</b> to the light valve <b>239</b> in turn. Through the light valve <b>239</b>, the monochromatic light beam <b>211</b> is converted to a monochromatic image. The monochromatic image is projected via the projection lens <b>230</b> onto a display screen (not shown). One skilled in the art may notice that red light, green light and blue light passes through the integrating rod <b>234</b>, the converging lens <b>236</b>, and the total internal reflection prism <b>238</b> in sequence to the light valve <b>239</b> within a frame period. Then, the light valve <b>239</b> converts the red light, green light and blue light into red image, green image and blue image to project a full color image onto the display screen through a projection lens <b>230</b>. Here, the light valve <b>239</b> is a digital micro-mirror device (DMD) or a Liquid Crystal on Silicon (LCoS), for example.

As shown in <figref idrefs="DRAWINGS">FIG. 2</figref>, the illumination module <b>210</b> further includes a signal transmitting device <b>217</b> and a signal sensing device <b>218</b>, for example. The signal transmitting device <b>217</b> is disposed on the color wheel <b>214</b> and the signal sensing device <b>218</b> is disposed at a suitable distance away from the signal transmitting device <b>217</b> for receiving a signal <b>217</b><i>a </i>from the signal transmitting device <b>217</b>.

It is noted that a plurality of color wheel indices K₁, K₂, . . . and so on are stored inside the controlling unit <b>216</b>. Furthermore, the controlling unit <b>216</b> is connected to the color wheel <b>214</b>, the signal sensing device <b>218</b>, and the light valve <b>239</b>. When the projection apparatus <b>200</b> receives an image signal, the control unit <b>216</b> computes the frequency of the image signal according to the rotational speed of the color wheel <b>214</b> and the frequency of the signal <b>218</b><i>a </i>selected by the signal sensing device <b>218</b>. Then, one of the color wheel indices that correspond to the frequency of the image signal is selected. According to the selected color wheel index, the light valve <b>239</b> is driven so that the tint and color level performance of an image projected from the projection apparatus can be improved.

To explain the function of the aforementioned projection apparatus, an embodiment is provided below so that the method of determining the aforementioned color wheel indices is also explained.

<figref idrefs="DRAWINGS">FIG. 3</figref> is a flow diagram showing steps for correcting the color level of a projection apparatus according to one preferred embodiment of the present invention. The correcting method is suitable for correcting the color level performance of an image projected from a projection apparatus with a color wheel. To implement the correcting method, a plurality of color wheel indices is input into the projection apparatus. In the present embodiment, referring to the <figref idrefs="DRAWINGS">FIG. 3</figref>, the steps for determining the color wheel indices are described in steps S<b>300</b> to S<b>304</b>. In step S<b>300</b>, a testing signal is input to the projection apparatus. Here, the range of the frequency of the testing signal is between 50 Hz to 150 Hz, for example.

Thereafter, step S<b>302</b> is carried out to adjust the color level of the testing signal so that the color level is smoothed out. Then, in step S<b>304</b>, the steps from S<b>300</b> to S<b>302</b> are repeated a number of times to obtain a plurality of color wheel indices corresponding to the testing signals at different frequencies.

After obtaining the color wheel indices, the step S<b>306</b> is carried out to input an image signal to the projection device. According to NTSC standard, the image signal is a 60 Hz signal with a digital RGB frequency between 60 Hz to 150 Hz, for example.

In step S<b>308</b>, a color wheel index that corresponds to the frequency of this image signal is selected so that the tint and color level performance of the image projected from the projection apparatus can be improved. The means of selecting the color wheel index in step S<b>308</b> includes a table look-up method, for example. In other words, the relationship between the color wheel indices and the frequency of the image signal is stored as a table within the projection apparatus.

In summary, a plurality of color wheel indices corresponding to the image signal at different frequencies is stored inside the projection apparatus. Hence, the projection apparatus automatically selects an appropriate color wheel index according to the received image signal so that the tint and color level performance of the image projected from the projection apparatus can be improved.

Moreover, because the projection apparatus of the present invention can automatically select a suitable color wheel index, there is no need to perform a manual adjustment of the color wheel index when switching the signal input source connected to the projection apparatus.

It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.